The present invention relates to an elevator position detector for an elevator system with a position detector for detecting digitally the position of a car and being controlled by its position detecting signal, in which a power source operable even in an abnormal condition such as power stoppage is provided and the correct position of the car is continuously stored and, when the power source is restored to a normal condition, it immediately initiates a normal operation of the elevator.
Generally, in an elevator control system, when abnormal condition of power source such as power stoppage takes place, it is placed in an emergency stoppage condition immediately to stop the car of elevator. Some amount of time is necessary till the car completely stops. Further, it is necessary to correctly detect and store the final position at which the car completely stops to perform an ordinary operation immediately after the power source is restored to its normal condition of operation. In the case of elevators installed in general office buildings, power is sometimes dropped for a relatively long time in the New Year or other consecutive holidays. Even in such a case, the elevator position detector must store the correct position of the car for a long period.
One of the conventional countermeasures for such the power trouble in the elevator control system is to use battery for the power source of the position detector to eliminate the power stoppage occurence. Another is to temporarily convert the electrical position signal to a mechanical position signal as of latching relays at the power stoppage and to store it and, when the power source returns to its normal operating condition, to reconvert the mechanical position signal to the original one. However, the former countermeasure is defective in that batteries with a large power capacity i.e. non-power stoppage power source, are necessary. The latter is defective in that the signal conversion mechanism is complex and the mechanical memory means is poor in space factor.
Recently, a rapid progress of digital integrated circuit technology produces a number of commercially available control circuits with a high integration density but low power consumption. Particularly, in the CMOS digital integrated circuits, its static current consumption of commercially available circuits is below 1 mA per package in the scale of MSI (medium scale integrated circuit).